Loading-coil.



TLSHAW. LQAD'ING COIL. V'APPucATlpN FILED' Nov. 5, 1914....

:Patnted Man-7, H216.

-2 SHEETS-SHEET' l.

.pa tent THOMAS SHAW., 0F HACKENSA'CK, NEW JERSEY, ASSIGNO, T0 AMERICAN TELEPHONE .ANB TELEGRAPH ClllllPjht',v A CORPORATION OF NEJV YORK.

LGAIDING-COIL.

Lit-L13?.

Application filed 'November 5, 19M.

T0 all 'whom 'it' may concer/n.'

Be it known that l., Tiroiras Eli-raw, residing at Hackensack, in they county of Bergen and State oit' New Jersey., have 1nvented certain .mprovements in Loading- Coils, ot which the following is ay specilication.

It has beenv found desirable in loading coils, ot' the continuous core or toroidal type employed in telephone lines, to torni gaps in the cores, thereby effecting an increase in what isternied the magnetic stability l, or that quality by virtue otywhich the inductance and resistance ot. the coil remain constant irrespective ot the variable magnetic history or experience ol the core. This result is due to the fact that the inagnetizing torce created by theit'ree poles at the ends of the core sections adjacentto the gaps opposes the magnetic torce which createsl it and also tends to neutralize the residual magnetism retained by the core after the removal ot the magnetiaing torce.

The purpose of the present invention is to reduce the electromagnetic andelectrostatic crosstalk existing in a coil. thus organized.

The invention is particularly applicable to duplex phantom loading coils in whichV thel line windings are arranged in sections upon quadrants of the core, in my joint with George A. Campbell, No. 980,921, dated January 10, ltlll, and in which the core Vitselil is divided into twe sections by diametricgaps. v

ln the acconniianying drawings7 Figure l shows diagran'nnatieally a phantom loading coil having its core. and winding-sections arranged in accordancewith the present invention; Fig. is a` diagrammatic illustration of the distribution of capacities .between the windings and core in such a coil; Fig. Slis a similar View showing the path -ot crosstalk current when shields are applied to the core; Fig. fr is an'enlarged irregular transverse section through one side ot' the coil withl the outer winding-section omitted; Fig. 5 shows in elevation the cere ot the coil with the electrostatic shields; and Fig. 6 shows the space relations between the ends ot the groups ot' winding-` Specification et Letters Patent.

Patented. Mai'. 7, 1916.

serial No. 370,425.

coil is shown, haif'ing pairs ot windings for insertion in conductors l0, ll and l2, 13 ot each ot' two physical telephone circuits. rl`he iron core ot this coilis. as illustrated, ot' the usual teroidal form and is divided at le, 14 by diametric gaps occupied by nonlnagnetic material. Upon the sections l5, l@ of the core thus termed, the line windings are arranged in sections 10, 10C, 11a, llc, l2", 12d, lbfand 13d, there being two sections for each line winding situated on opposite coreqiradrants c, Z, c, and (Z, each section extending from a point in proximity to one ot the gaps ll to a point adjacent to the center of the core section. To prevent electromagnetic crosstalk in the coil between the two physical circuits, the windings included in said circuits must be electromagnetically balanced,v and this requires that the mutual impedances between the winding-sections separated by the core gaps shall be equal to the mutual impcdances between those on the saine section. In the manufacture o't' loading coils haring pluralsection cores7 it is necessaryv to'leare an appreciable space between the windings to allow tor cutting the core; and between the gaps, in the two-section core coil carrying tour groups ot winding-sections such as is now being described, the windings are naturally put as closely together as is consistent with the requiren'ients of dielectric strength to economize ,winding space. The presence or' the gaps and the separation of the windings at thesevpoints leads to considerable magnetic leakage.y causing mutual impedance imbalance between the windings and consequent crosstalk. .ln accordainfe with this invention, the leakage at the extremities ot the winding-sections is, as tar as practicable, equalized, and approximate electromagnetic balance is therefore attained and crosstalk from this source becomes almost negligible. This is accomplished in two ways; Vthe (ends of the winding-sections at opposite sides ot the gaps are brought as closely together as is possible, and yet leave space to cut through the Vcore without injuring the windings. 'lhisminimizes the leakage at these points. ln a standard loading coil this separation between the windings inay be as little as one eighth of an inch. At'ninety degrees from the gaps, the opposite extremities ot the windings are separated at 17, by, say, from an eighth to a quarter Ot an inch,l

creating poles Which have similar leakage effects to the core gaps. .Just what this `leakage-equalizing spacing ofthe windings shall be dependsv upon various considerations, as gap and core proportions and coil inductance.

The use of two diametric core-gaps, unless means were taken to prevent it, would lead to electrostatic crosstalk between the side circuits by way oitl the capacities Ica, 7u, 7c and lcd between the inner layers of the winding-sections which are next the core and Coresections. The distribution of these windingto-core admittances appears in Fig. 2. Itl

-will be seen that k and lab are associated with thecore sectionl and la and /cd' with the other section. Tle circuit 10, 11 is considered as the disturbing side circuit, the

.. flow ot' current therein being indicated by long arrows. ,The path for crosstalk, shown by the short arrowsyis as follows: from the conductor 10 by way of winding-section 10a through capacityy` lua, the core quadrants a and and capacity cb to the winding-section 12b, where thecurrent divides and iiows in opposite directions through the conductor'A -12 of the disturbed side-circuit, back over the other conductor 13 of this side circuit to the winding-section 13d, through the ca- -paeity lcd., quadrants Z and c and capacity la@ to the winding-section 11 and the conductor 11 of the disturbing side circuit. Disturbing current will How inthe circuit indicated because the capacities k and v10 are associated with the opposite conductors ot' the same side circuit and will thus have its full potential acting upon it.' This electrostatic crosstalk may be eliminated by applying' to each core-section an electrostatic shield 21 (Figs. -L and 5) and conductively connecting these at 22. The shields may consist ot' thin metallic sheets, as copper net'- ting or tin foil, wrapped about vthe .core-sec-l tions with the adjacent edges extending circumfercntially of the lcore. A These edges should be separated or insulatedfrom one another at 23, so that they shall not fur- A nish a closed electrical circuit about the core acting as a slwi't-cii'ciiited secondary winding thereof. The connections 22 must be of non-magnetic metalto avoid short-circuiting the gaps in the core and-is preferably soldered to the shields at eachextremity.

The low resistance connectionsbetween the.

shields short-circuit the high impedance crosstalk paths in the manner shown by the short arrows in Fig. 3.

l claim:v

l. In av loading coil, core-sections separated by gaps, and a plurality of separate winding-sections on each core-section,-one winding-section on one partof a core-section being separated by a gap from another winding-section on another part of said core-section, the extent of separation between the winding-sections tending to equalize their mutual impedances.

2l In a loading coil. core-sectionsseparated by, gaps, and a plurality oli windingsections on each core-section and separated from oneanother at the gaps and between said gaps, the relation Abetween the ends of the winding-sections tending to equalize magnetic leakage.

A generally toroidal core provided with diametric gaps separating it into two sections, and two groups or' winding-sections `arranged on each section of the core, the sepf aration between the groups of winding-secrality of sections, a sheet of conductive material surrounding each section with the ad- Jacent edges of each sheet vextending circumterentially of the core and beinginsulated from one another, a conductive connection between the shields of different sections,'and windings outside the shields.

in testimony whereof, l'ha've signed my name to this specification in .they presence of two subscribing witneses, this twenty slxt day of Obtober 1914.

lTnoinis SHAW.

Witnesses z LLOYD Esrnxscinnn, Vilar/run J. Donen. 

